Investigating an alternative ring design of transducer arrays for Tumor Treating Fields (TTFields)

Tumor treating fields (TTFields) is a therapy that inhibits cell proliferation and has been approved by the U.S Food and Drug Administration (FDA) for the treatment of Glioblastoma Multiforme. This anti-mitotic technique works non-invasively and regionally, and is associated with less toxicity and a better quality of life. Currently a device called Optune (TM) is clinically used which works with two perpendicular and alternating array pairs each consisting of 3x3 transducers. The aim of this study is to investigate a theoretical alternative array design which consists of two rings of 16 transducers and thus permits various field directions. A realistic human head model with isotropic tissues was used to simulate the electric field distribution induced by the two types of array layouts. One virtual tumour was modelled as a sphere in the white matter close to one lateral ventricle. Four alternative ring design directions were evaluated by activating arrays of 2x2 transducers on opposite sides of the head. The same amount of current was passed through active transducer arrays of the Optune system and the ring design. The electric field distribution in the brain differs for the various array configurations, with higher fields between activated transducer pairs and lower values in distant areas. Nonetheless, the average electric field strength values in the tumour are comparable for the various configurations. Values between 1.00 and 1.91 V/cm were recorded, which are above the threshold for effective treatment. Increasing the amount of field directions could possibly also increase treatment efficacy, because TTFields' effect on cancer cells is highest when the randomly distributed cell division axis is aligned with the field. The results further predict that slightly changing transducer positions only has a minor effect on the electric field. Thus patients might have some freedom to adjust array positions without major concern for treatment efficacy.